[ATTACH=full]2165[/ATTACH] [ATTACH=full]2166[/ATTACH]

s=-6cos((pi*t)/6) t=1 is incorrect (gives you s= -3sqrt(3)) t=3 is correct t=5 is incorrect (gives you s= 3sqrt(3)) t=7 is incorrect (gives you s= 3sqrt(3)) t=9 is correct t=11 is incorrect (gives you s= -3sqrt(3)) so, t=3,9,15,21 is correct if you did the table first would be better